The present invention relates to a method for preparing polycarbonates by a transesterification reaction between, for example, diaryl carbonate and aromatic bis hydroxy compounds. In particular, this invention relates to the melt polymerization reaction for the preparation of polycarbonates and novel polycarbonate catalysts comprised of certain Ruthenium compounds and complexes.
A large number of catalyst systems have been examined for application to the melt polymerization of polycarbonates. Most of these methods require either a variety of co-catalysts or the subsequent addition of a catalyst quencher to ensure polymer stability. The need for high purity, high quality thermoplastic resins requires the reduction of residual contaminants in the final resin. This need for very low residual impurities is particularly acute in optical quality (OQ) grade polycarbonate resins. One approach towards elimination of residual solvent contamination, particularly methylene chloride, is through the implementation of a solventless (i.e., melt) process.
The melt process generally involves a base catalyzed condensation polymerization of, for example, diphenyl carbonate, and a dihydroxy compound such as Bisphenol A. The reaction is conducted at high enough temperatures for the starting monomers and product to remain molten, while the reactor pressure is staged in order to effectively remove phenol, the by-product of the polycondensation reaction.
Most current melt technology programs employ a two component catalyst system. The first component is a tetralkylammonium hydroxide (TMAH) co-catalyst which is used to initiate oligomer formation in the melt. The second catalyst is an alkali metal hydroxide which is the second part of the overall catalyst system. Due to its intrinsic thermal stability, the alkali metal salt must be quenched at the end of the polymerization. This quenching process requires the addition of yet another component to the polymer formation. All materials from the quenching process remain in the final resin, further compromising the final properties.
Although the alkali metal hydroxides in general are excellent melt polymerization catalysts they tend to generate substantial amounts of an additional undesired by-product which is a branched polycarbonate species typically referred to as Fries product which has the repeat unit as set forth below. The formation of Fries product during melt polycarbonate polymerization leads to changes in ductility and in general rheological properties of the polymer. Polycarbonates produced by the melt process typically have higher Fries content than polycarbonates produced by the interfacial method. As used herein the term Fries or fries refers to a repeating unit in polycarbonate having the following formula: ##STR1##
wherein the X variable represents ##STR2## PA1 wherein variables R.sub.c and R.sub.d each independently represent a hydrogen atom PA1 [Ru(phenyl).sub.3 ].sub.2.sup.+ 2X.sup.-, [Ru(phenyl).sub.3 ].sub.2.sup.+ 2Cl.sup.-, [Ru(phenyl).sub.3 ].sub.2.sup.+ 2Br.sup.-, [Ru(bipyridyl).sub.3 ].sub.2.sup.+ 2X.sup.-, [Ru(biphenyl).sub.3 ].sub.2.sup.+ 2Cl.sup.-, [Ru(bipyridyl).sub.3 ].sub.2.sup.+ 2Br.sup.-, [Ru(bipyridyl).sub.3 ].sub.2.sup.+ 2X.sup.- [Ru(bipyridyl).sub.3 ].sub.2.sup.+ 2Cl.sup.-, [Ru(bipyridyl).sub.3 ].sub.2.sup.+ 2 Br.sup.-, [Ru(3,3"dihydroxy 2,2"bipyridine].sub.3 ].sub.2.sup.+ 2X.sup.-, [Ru(3,3"dihydroxy 2,2"bipyridine].sub.3 ].sub.2.sup.+ 2Cl.sup.-, [Ru(3,3"dihydroxy 2,2"bipyridine].sub.3 ].sub.2.sup.+ 2Br.sup.-, [Ru(1,10 phenanthroline).sub.3 ].sub.2.sup.+ 2X.sup.-, [Ru(1,10 phenanthroline).sub.3 ].sub.2.sup.+ 2Cl.sup.-, [Ru(1,10 phenanthroline).sub.3 ].sub.2.sup.+ 2Br.sup.-, [Ru(phenanthroline 5,6-diimine).sub.3 ].sub.2.sup.+ 2X.sup.-, [Ru(phenanthroline 5,6-diimine).sub.3 ].sub.2.sup.+ 2Cl.sup.-, [Ru(phenanthroline 5,6-diimine).sub.3 ].sub.2.sup.+ 2Br.sup.-, [Ru(4,4"dicarboxy-2,2"bipyridine).sub.3 ].sub.2.sup.+ 2X.sup.-, [Ru(4,4"dicarboxy-2,2"bipyridine){character pullout}].sub.2.sup.+ 2Cl.sup.-, [Ru(4,4"dicarboxy-2,2"bipyridine){character pullout}].sub.2.sup.+ 2Br.sup.-, [Ru(4,4"dimethyl-2,2"bipyridine).sub.3 ].sub.2.sup.+ 2X.sup.-, [Ru(4,4"dimethyl-2,2"bipyridine).sub.3 ].sub.2.sup.+ 2Cl.sup.-, [Ru(4,4"dimethyl-2,2"bipyridine).sub.3 ].sub.2.sup.+ 2Br.sup.-, [Ru(bipyrazyl).sub.3 ].sub.2.sup.+ 2X.sup.-, [Ru(bipyrazyl){character pullout}].sub.2.sup.+ 2Cl.sup.-, and [Ru(bipyrazyl){character pullout}].sub.2.sup.+ 2Br.sup.-. PA1 wherein: R is independently selected from halogen, monovalent hydrocarbon, and monovalent hydrocarbonoxy radicals; R.sup.1 is independently selected from halogen, monovalent hydrocarbon, and monovalent hydrocarbonoxy radicals; and wherein n and n.sup.1 are independently selected from integers having a value of from 0 to 5 inclusive. PA1 wherein D is a divalent aromatic radical. Preferably, D has the formula: ##STR4## PA1 wherein A.sup.1 represents an aromatic group such as phenylene, biphenylene, naphthalene and the like; E represents an alkylene or alkylidene group such as methylene, ethylene, ethylidine, propylene, propylidene, isopropylidene, butylene, isobutylene, amylene, isoamylidene, and the like. Where E is an alkylene or alkylidene group, it may also consist of two or more alkylene or alkylidene groups connected by a moiety different from alkylene or alkylidene, such as an aromatic linkage; a tertiary amino linkage; an ether linkage; a carbonyl linkage; a silicon-containing linkage; or a sulfur-containing linkage such as sulfide, sulfoxide, sulfone, etc.; or a phosphorus-containing linkage such as phosphinyl, phosphonyl, etc. In addition, E may be a cycloaliphatic group (e.g., cyclopentylidene, cyclohexylidene, 3,3,5-trimethylcyclohexylidene, methylcyclohexylidene, 2-[2,2,1]-bicycloheptylidene, neopentylidene, cyclopentadecylidene, cyclodecylidene, adamantylidene, and the like); a sulfur-containing linkage, such as sulfide, sulfoxide or sulfone; a phosphorus-containing linkage, such as phosphinyl, phosphonyl; an ether linkage; a carbonyl group; a tertiary nitrogen group; or a silicon-containing linkage such as silane or siloxy. R.sup.2 represents hydrogen or a monovalent hydrocarbon group such as alkyl, aryl, aralkyl, alkaryl, or cycloalkyl. Y.sup.1 may be an inorganic atom such as halogen (fluorine, bromine, chlorine, or iodine); an inorganic group such as nitro; an organic group such as R.sup.2 above, or an oxy group such as OR.sup.2. It is only necessary that Y.sup.1 be inert to and unaffected by reactants and reaction conditions used to prepare the polycarbonate. The letter m represents any integer from and including zero through the number of positions on A.sup.1 available for substitution; p represents an integer from and including zero through the number of positions on E available for substitution; t represents an integer equal to at least one; s is either zero or one; and u represents zero or any integer. PA1 wherein X.sup.- is a counterion; (b) [RuH(1,2 bis(diphenylmethyl benzene).sub.2 ].sup.+ 2X.sup.- ; (c) [RuH(1,2 bis(diphenylmethyl benzene).sub.2 ].sup.+ 2Br.sup.- ; or [RuH(1,2 bis (diphenylmethyl benzene).sub.2 ].sup.+ 2Cl.sup.- ; (d) Ru(II) porphyrin dimers and tetramers; (e) 2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphine ruthenium(II) carbonyl; (f) Pentamethylcyclopentadienylruthenium(III) chloride polymer; (g) Dichloro(1,5-cyclooctadiene) ruthenium(II); (h) Tetrakis(dimethylsulfoxide)dichlororuthenium(II); (i) Potassium hydroxytetranitronitrosoruthenate(II); (k) Ruthenium nitroso hydroxide; (I) Ruthenium(III) iodide; (m) Ruthenium(III) nitrosylnitrate; (n) Pentaaminechlororuthenium(III) dichloride; (o) Dichlorotricarbonylruthenium(II) dimer; (p) Dicarbonyldichlorobis(triphenylphosphine)ruthenium(II); (q) Bis (cyclopentadienyl)ruthenium; (r) Potassium hexacyanoruthenate(II) trihydrate; (s) Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)ruthenium(III); (t) Chloro(lndenyl)Bis (triphenylphosphine) Ruthenium(III); (2C.sub.18 H.sub.15 PC.sub.9 H.sub.7 ClRu); and (u) Ruthenium(III) acetylacetonate; optionally in the presence of a co-catalyst selected from tetraalkyl ammonium and tetraalkyl phosponium salts; (II) oligomerizing the product from step (a) in a reaction system comprising at least one continuous reactor in series, wherein said reactor is operated at a temperature of about 210.degree. C. to about 290.degree. C., and wherein the product from the reactor has a number average molecular weight of about 1000 to about 5500; and (III) polymerizing the product from step (b) in a reaction system comprising at least one continuous polymerization reactor in series, wherein said reactor is operated at a temperature of about 280.degree. C. to 315.degree. C., wherein the product from step (c) has a number average molecular weight of at least about 6500.
or a monovalent hydrocarbon group and may form a ring structure.
Thus, a need exists for the development of alternative melt polycarbonate polymerization catalysts which produce less Fries product than conventional catalyst systems.